Source-to-sink tandem geochronology reveals tectonic influences on the Cambrian Transcontinental Arch of Laurentia

Abstract

Competing hypotheses attribute the regional loss of 1.2–1.0 Ga detrital zircon from the Cambrian Sauk Sequence in southwestern North America to differing tectonic controls on surface topography. We test three hypotheses with source-to-sink detrital zircon provenance analysis via tandem in situ and isotope dilution U–Pb geochronology paired with geochemical and Hf-isotope tracers. Our data indicate that the lower-to-middle Sixtymile Formation in Grand Canyon was derived from ca. 1.1 Ga rocks of the Llano Uplift and the ca. 539–523 Ma Wichita igneous province, approximately 1400 km away. In contrast, new U–Pb geochronology links the upper Sixtymile and Tapeats formations to the 513–510 Ma Florida Mountains intrusive complex, southern New Mexico, and proximal 1.4 and 1.7 Ga basement approximately 650 km away. We attribute a regional provenance shift to plume–lithosphere interactions on the Iapetan margin, tectonism along ‘leaky’ intracratonic transverse fault zones and the rift-to-drift transition on the Cordilleran margin.